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Caractérisation et susceptibilité aux effondrements dans un karst de contact lithostratigraphique : l'exemple du barrois

Abstract : The present study consisted in assessing the risk of karstic collapse in a very karstified sector of the Barrois, 37 km2 in area, the forest of Trois-Fontaines sensu lato (Meuse / Haute-Marne/ Marne - France), located in contact with Jurassic limestones and the clayey-sandy and calcareous cover of the Lower Cretaceous. This research, which is part of the Cavities Plan piloted by BRGM, has made it possible to specify the modalities of karstic collapse hazard in a lithostratigraphic contact karst in contact with Barrois Limestones (Tithonian) or Spatangian Limestones (Hauterivian) and Neocomian clays, notably Oyster Clay (Lower Barrémien). Mapping and measurements carried out in the field and punctual LiDAR images have revealed the presence of 2700 karstic disorders, essentially dolines, organized in sinuous lines following the topography. The types of karstic forms and phenomena have highlighted two main types of processes at the origin of the dolines: the draining and the collapse. Withdrawal sinkholes, marked by subvertical slopes, are conditioned by the existence of cavities in the Tithonian limestones generated by the incision of rivers and the hydraulic gradient; or/and, the withdrawal of Valanginian clays and sands causing a void under the Spatangian Limestones, and their collapse, weakened by the multiple alternations of sandy or non-sandy limestones and marly and sandy banks.The susceptibility map was established using the method of the "weight of evidence" theory, a Bayesian theory that assigns weights for each of the criteria: (i) high susceptibility assigned to lithostratigraphic contact karst; (ii) medium susceptibility in sectors with slopes equal to and greater than 4°; (iii) medium susceptibility for sectors within 50 m of a watercourse; (iv) low susceptibility assigned regardless of distance from faults.This method and the type of susceptibility maps that also exist abroad, such as in Wallonia and Florida, are an important tool for the consideration and prevention of karst risks.
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http://docnum.univ-lorraine.fr/ulprive/DDOC_T_2020_0292_BENSAADI.pdf
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Submitted on : Wednesday, June 2, 2021 - 4:53:55 PM
Last modification on : Thursday, June 3, 2021 - 3:29:29 AM

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  • HAL Id : tel-03246973, version 1

Citation

Kamila Bensaadi. Caractérisation et susceptibilité aux effondrements dans un karst de contact lithostratigraphique : l'exemple du barrois. Géographie. Université de Lorraine, 2020. Français. ⟨NNT : 2020LORR0292⟩. ⟨tel-03246973⟩

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